Add player and board size meta data to all game maps (#84)

* WIP: initial data model for new meta props
* WIP: implemented new props
* test and bug fix:
- add coverage of players and sizes
- fix unlimited map size bug
* FIX: update supported players for arcade to 6
* fix: test should be min -> max, not max->max
* Change some naming and the FixedSizes function
* update comment to reflect API changes
* improve comment clarity
* rename field for improved clarity
* change some more "map" -> "board" wording

maps/arcade_maze.go

@@ -20,6 +20,9 @@ func (m ArcadeMazeMap) Meta() Metadata {
 		Description: "Generic arcade maze map with deadly hazard walls.",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  6,
+		BoardSizes:  FixedSizes(Dimensions{19, 21}),
 	}
 }
 

maps/empty.go

@@ -20,6 +20,9 @@ func (m EmptyMap) Meta() Metadata {
 		Description: "Default snake placement with no food",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 

maps/game_map.go

@@ -18,6 +18,41 @@ type GameMap interface {
 	UpdateBoard(previousBoardState *rules.BoardState, settings rules.Settings, editor Editor) error
 }
 
+// Dimensions describes the size of a Battlesnake board.
+type Dimensions struct {
+	// Width is the width, in number of board squares, of the board.
+	// The value 0 has a special meaning to mean unlimited.
+	Width uint
+	// Height is the height, in number of board squares, of the board.
+	// The value 0 has a special meaning to mean unlimited.
+	Height uint
+}
+
+// sizes is a list of board sizes that a map supports.
+type sizes []Dimensions
+
+// IsUnlimited reports whether the supported sizes are unlimited.
+// Note that even for unlimited sizes, there will be an upper bound that can actually be run and visualised.
+func (d sizes) IsUnlimited() bool {
+	return len(d) == 1 && d[0].Width == 0
+}
+
+// AnySize creates sizes for a board that has no fixed sizes (supports unlimited sizes).
+func AnySize() sizes {
+	return sizes{Dimensions{Width: 0, Height: 0}}
+}
+
+// FixedSizes creates dimensions for a board that has 1 or more fixed sizes.
+// Examples:
+// - FixedSizes(Dimension{9,11}) supports only a width of 9 and a height of 11.
+// - FixedSizes(Dimensions{11,11},Dimensions{19,19}) supports sizes 11x11 and 19x19
+func FixedSizes(a Dimensions, b ...Dimensions) sizes {
+	s := make(sizes, 0, 1+len(b))
+	s = append(s, a)
+	s = append(s, b...)
+	return s
+}
+
 type Metadata struct {
 	Name        string
 	Author      string
@@ -25,6 +60,15 @@ type Metadata struct {
 	// Version is the current version of the game map.
 	// Each time a map is changed, the version number should be incremented by 1.
 	Version uint
+	// MinPlayers is the minimum number of players that the map supports.
+	MinPlayers uint
+	// MaxPlayers is the maximum number of players that the map supports.
+	MaxPlayers uint
+	// BoardSizes is a list of supported board sizes. Board sizes can fall into one of 3 categories:
+	//   1. one fixed size (i.e. [11x11])
+	//   2. multiple, fixed sizes (i.e. [11x11, 19x19, 25x25])
+	//   3. "unlimited" sizes (the board is not fixed and can scale to any reasonable size)
+	BoardSizes sizes
 }
 
 // Editor is used by GameMap implementations to modify the board state.

maps/game_map_test.go

@@ -62,3 +62,18 @@ func TestBoardStateEditor(t *testing.T) {
 	editor.ClearHazards()
 	require.Equal(t, []rules.Point{}, boardState.Hazards)
 }
+
+func TestMapSizes(t *testing.T) {
+	s := FixedSizes(Dimensions{11, 12})
+	require.Equal(t, s[0].Width, uint(11))
+	require.Equal(t, s[0].Height, uint(12))
+
+	s = FixedSizes(Dimensions{11, 11}, Dimensions{19, 25})
+	require.Len(t, s, 2)
+	require.Equal(t, s[1].Width, uint(19))
+	require.Equal(t, s[1].Height, uint(25))
+
+	s = AnySize()
+	require.Len(t, s, 1, "unlimited maps should have just one dimensions")
+	require.True(t, s.IsUnlimited())
+}

maps/hazards.go

@@ -30,6 +30,9 @@ func (m InnerBorderHazardsMap) Meta() Metadata {
 		Description: "Creates a static map on turn 0 that is a 1-square wall of hazard that is inset 2 squares from the edge of the board",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -67,6 +70,9 @@ func (m ConcentricRingsHazardsMap) Meta() Metadata {
 		Description: "Creates a static map where there are rings of hazard sauce starting from the center with a 1 square space between the rings that has no sauce",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -105,6 +111,9 @@ func (m ColumnsHazardsMap) Meta() Metadata {
 		Description: "Creates a static map on turn 0 that fills in odd squares, i.e. (1,1), (1,3), (3,3) ... with hazard sauce",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -141,6 +150,9 @@ func (m SpiralHazardsMap) Meta() Metadata {
  the map. Each 2 turns a new hazard square is added to the map`,
 		Author:     "altersaddle",
 		Version:    1,
+		MinPlayers: 1,
+		MaxPlayers: 8,
+		BoardSizes: AnySize(),
 	}
 }
 
@@ -230,6 +242,9 @@ func (m ScatterFillMap) Meta() Metadata {
 		Name:        "hz_scatter",
 		Description: `Fills the entire board with hazard squares that are set to appear on regular turn schedule. Each square is picked at random.`,
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -278,6 +293,9 @@ func (m DirectionalExpandingBoxMap) Meta() Metadata {
 		Name:        "hz_grow_box",
 		Description: `Creates an area of hazard that expands from a point with one random side growing on a turn schedule.`,
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -389,6 +407,9 @@ func (m ExpandingBoxMap) Meta() Metadata {
 		Name:        "hz_expand_box",
 		Description: `Generates an area of hazard that expands from a random point on the board outward in concentric rings on a periodic turn schedule.`,
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -461,6 +482,9 @@ func (m ExpandingScatterMap) Meta() Metadata {
 		Name:        "hz_expand_scatter",
 		Description: `Builds an expanding hazard area that grows from a central point in rings that are randomly filled in on a regular turn schedule.`,
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 
@@ -540,6 +564,9 @@ func (m RiverAndBridgesHazardsMap) Meta() Metadata {
 Each river has one or two 1-square "bridges" over them`,
 		Author:     "Battlesnake",
 		Version:    1,
+		MinPlayers: 1,
+		MaxPlayers: 8,
+		BoardSizes: FixedSizes(Dimensions{11, 11}, Dimensions{19, 19}, Dimensions{25, 25}),
 	}
 }
 

maps/registry_test.go

@@ -23,9 +23,42 @@ func TestRegisteredMaps(t *testing.T) {
 	for mapName, gameMap := range globalRegistry {
 		t.Run(mapName, func(t *testing.T) {
 			require.Equalf(t, mapName, gameMap.ID(), "%#v game map doesn't return its own ID", mapName)
-			require.True(t, gameMap.Meta().Version > 0, fmt.Sprintf("registered maps must have a valid version (>= 1) - '%d' is invalid", gameMap.Meta().Version))
+			meta := gameMap.Meta()
+			require.True(t, meta.Version > 0, fmt.Sprintf("registered maps must have a valid version (>= 1) - '%d' is invalid", meta.Version))
+			require.NotZero(t, meta.MinPlayers, "registered maps must have minimum players declared")
+			require.NotZero(t, meta.MaxPlayers, "registered maps must have maximum players declared")
+			require.LessOrEqual(t, meta.MaxPlayers, meta.MaxPlayers, "max players should always be >= min players")
+			require.NotEmpty(t, meta.BoardSizes, "registered maps must have at least one supported size declared")
 			var setupBoardState *rules.BoardState
 
+			// "fuzz test" supported players
+			mapSize := pickSize(meta)
+			for i := meta.MinPlayers; i < meta.MaxPlayers; i++ {
+				t.Run(fmt.Sprintf("%d players", i), func(t *testing.T) {
+					initialBoardState := rules.NewBoardState(int(mapSize.Width), int(mapSize.Height))
+					for j := uint(0); j < i; j++ {
+						initialBoardState.Snakes = append(initialBoardState.Snakes, rules.Snake{ID: fmt.Sprint(j), Body: []rules.Point{}})
+					}
+					err := gameMap.SetupBoard(initialBoardState, testSettings, NewBoardStateEditor(initialBoardState))
+					require.NoError(t, err, fmt.Sprintf("%d players should be supported by this map", i))
+				})
+			}
+
+			// "fuzz test" supported map sizes
+			if !meta.BoardSizes.IsUnlimited() {
+				for _, mapSize := range meta.BoardSizes {
+					t.Run(fmt.Sprintf("%dx%d map size", mapSize.Width, mapSize.Height), func(t *testing.T) {
+						initialBoardState := rules.NewBoardState(int(mapSize.Width), int(mapSize.Height))
+						for i := uint(0); i < meta.MaxPlayers; i++ {
+							initialBoardState.Snakes = append(initialBoardState.Snakes, rules.Snake{ID: fmt.Sprint(i), Body: []rules.Point{}})
+						}
+						err := gameMap.SetupBoard(initialBoardState, testSettings, NewBoardStateEditor(initialBoardState))
+						require.NoError(t, err, "error setting up map")
+					})
+				}
+			}
+
+			// Check that at least one map size can be setup without error
 			for width := 0; width < maxBoardWidth; width++ {
 				for height := 0; height < maxBoardHeight; height++ {
 					initialBoardState := rules.NewBoardState(width, height)
@@ -67,3 +100,13 @@ func TestRegisteredMaps(t *testing.T) {
 		})
 	}
 }
+
+func pickSize(meta Metadata) Dimensions {
+	// For unlimited, we can pick any size
+	if meta.BoardSizes.IsUnlimited() {
+		return Dimensions{Width: 11, Height: 11}
+	}
+
+	// For fixed, just pick the first supported size
+	return meta.BoardSizes[0]
+}

maps/royale.go

@@ -22,6 +22,9 @@ func (m RoyaleHazardsMap) Meta() Metadata {
 		Description: "A map where hazards are generated every N turns",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }
 

maps/standard.go

@@ -20,6 +20,9 @@ func (m StandardMap) Meta() Metadata {
 		Description: "Standard snake placement and food spawning",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  8,
+		BoardSizes:  AnySize(),
 	}
 }